Cos^2 x - cos(2x) = 0,5 cos(2x) = cos^2 x - sin^2 x sin^2 x = 1 - cos^2 x cos(2x) = cos^2 x - (1 - cos^2 x) = cos^2 x - 1 + cos^2 x = 2*cos^2 x - 1 cos^2 x - (2*cos^2 x - 1) = 0,5 cos^2 x - 2*cos^2 x + 1 = 0,5 -cos^2 x = 0,5 - 1 -cos^2 x = -0,5 cos^2 x = 1/2 1) cos x = 1/√(2) cos x = √(2)/2 x = π/4 + 2πn ; x = -π/4 + 2πn 2) cos x = -1/√(2) cos x = -√(2)/2 x = 3π/4 + 2πn ; x = -3π/4 + 2πn ответ: х = π/4 + 2πn ; x = -π/4 + 2πn ; 3π/4 + 2πn ; x = -3π/4 + 2πn.
